1. Field of the Invention
The present invention relates generally to multilayer circuit boards, and more particularly to multilayer circuit boards having air bridge circuits.
2. Disclosure Information
In the printed circuit board (PCB) industry, various methods are used to produce multilayer (i.e., two-or-more-layer) PCBs. U.S. Pat. Nos. 4,404,059 to Livshits et al. (hereinafter xe2x80x9cLivshitsxe2x80x9d) and 5,738,797 to Belke et al. (hereinafter xe2x80x9cBelkexe2x80x9d), both of which are incorporated herein by reference, describe xe2x80x9cadditivexe2x80x9d processes for PCB construction, while U.S. Pat. No. 3,801,388 to Akiyama et al. (hereinafter xe2x80x9cAkiyamaxe2x80x9d), also incorporated herein by reference, teaches a xe2x80x9csubtractivexe2x80x9d process for PCB manufacture. These additive and subtractive processes involve various masking, plating, mask-stripping, chemical etching, and other steps for constructing multilayer circuit boards having features known as xe2x80x9cair bridgesxe2x80x9d, xe2x80x9ccrossoversxe2x80x9d, xe2x80x9cair bridge crossoversxe2x80x9d, and the like.
Air bridge crossover circuits are useful for creating high density circuits. However, such circuits sometimes suffer from susceptibility to mechanical damage, caused by physical impact, thermal excursions, and the like. It would be desirable, therefore, to provide a way of creating such multilayer air bridge circuits without this drawback.
The present invention overcomes the disadvantages of the prior art approaches by providing a multilayer air bridge circuit structure, and method for producing the same, which has special metallic fortifying layers which mitigate the aforementioned disadvantages.
It is an object and advantage that the present invention includes an air bridge circuit having metallic fortifying layers which mechanically and/or electrically enhance the circuit.
Another advantage is that the present invention may be easily and economically incorporated into both the additive and subtractive air bridge circuit construction processes.
These and other advantages, features and objects of the invention will become apparent from the drawings, detailed description and claims which follow.